by Ken Task.
The 'server has gone away' is typical of MySQL config where the value for max_allowed_packets is too small. In your my.cnf (config file for mysqld) under the [mysqld] section (assumes Linux config file), insert:
max_allowed_packets=500M
The value is a guess but be sure to include the 'M' designator.
Restart MySQL service after making the change.
Then try your backup again - still leaving debug on in case there is something else.
'spirit of sharing', Ken